$A$ magnetic needle suspended by a silk thread is vibrating in the earth's magnetic field. If the temperature of the needle is increased by $500^{\circ}C$,then

The materials suitable for making electromagnets should have

The magnetic property of a magnetic substance is associated with

There are four light-weight rod samples $A, B, C, D$ separately suspended by threads. $A$ bar magnet is slowly brought near each sample and the following observations are noted:
$(i)$ $A$ is feebly repelled
$(ii)$ $B$ is feebly attracted
$(iii)$ $C$ is strongly attracted
$(iv)$ $D$ remains unaffected
Which one of the following is true?

$A$ soft ferromagnetic material is placed in an external magnetic field. The magnetic domains:

For a permanent magnet,which of the following properties is essentially required?